Commercial ice making machines are designed to operate continuously and for extended periods of time. To operate efficiently, water must flow rapidly through the machine and high heat transfer rates must be maintained to freeze the water and form ice. Under such operating conditions, any loss of fluid flow or reduction in heat transfer rates can retard ice production and increase the operating cost of the ice machine.
The water recirculation and ice forming systems commonly found in commercial ice making equipment primarily includes a water supply, a water reservoir or water sump, and a means for discarding excess water from the circulating water system, such as a drain or overflow system. A water circulation or recirculation pump or other means is provided for circulating water through the water/ice system. In one type of delivery system, water is pumped to a water distributor for distributing the circulated water across an evaporator plate. In another type of system, water is sprayed onto an evaporator plate. The evaporator plate is usually equipped with a water curtain to direct the water flowing from the water distributor over the evaporator and to distribute unfrozen water back into the water sump. In one type of ice machine, an ice thickness sensing probe for detecting the thickness of the ice formed on the evaporator plate is attached to the evaporator so as to terminate a freeze cycle when sufficient ice is formed and to begin a harvest cycle. In another type of machine, water level sensors are employed to detect when the water level in the water sump falls to a predetermined level, indicating that it is time to harvest the ice.
After the ice has been formed to a desired thickness, a harvest system is initiated, which stops the flow of coolant to the evaporator plate and begins an ice recovery process. To harvest the ice formed on the evaporator, hot refrigerant gas or cool vapor is directed into the evaporator to heat the evaporator plate and release the ice. The ice falls into an ice collector reservoir. An improved harvest system is disclosed in commonly-assigned U.S. Pat. Nos. 6,196,007 and 6,705,107, the disclosures of which are incorporated by reference herein.
Ice making machines that run automatically and for extended periods of time are prone to fouling from environmental sources. During extended use, the water recirculation and ice forming system accumulates soil and water hardness components, such as calcium carbonate and magnesium salts, on the interior surfaces of the system. Occasionally, depending upon the environment in which the ice making machine is located and the quality of the water supplied to the ice making machine, various biological deposits can form, including microbiological growths, yeast residues and slimes. These deposits can possibly become dissolved or entrained in condensate that forms on the evaporator and contaminate the water used to form ice.
Further, soil, water hardness, and biological deposits formed on interior surfaces impede the flow of water through the system and decrease the heat transfer efficiency of the evaporator plate. To maintain operating efficiency the system and sanitary conditions surfaces have to be cleaned to remove the deposits. The cleaning process normally requires dismantling that portion of the ice making machine containing the contaminated surfaces and washing and scrubbing the surfaces using acidic cleaner solutions. After cleaning, care must be taken to rinse the cleaning solution from the surfaces to avoid becoming frozen into the ice that is subsequently formed on the cleaned surfaces. Care must also be taken to avoid contamination of the water supply within the machine that is used to form ice. Then, the machine must be reconstructed. The cleaning process is labor intensive, costly, and inefficient.
To reduce the frequency of disassembly, injection cleaning methods can be used. Injecting cleaning involves injecting an acid solution into the circulating water and manually turning off the coolant system. These cleaning methods can, however, also include auto-cleaning techniques as disclosed in commonly-assigned U.S. Pat. Nos. 5,289,691; 5,408,834; 5,586,439; and 5,752,393, the disclosures of which are incorporated by reference herein. When fouled surfaces are washed with the acidic cleaners, however, the acid comes in contact with metal surfaces, which eats away metal surfaces, such as the evaporator plate. The metal surfaces contain metals and metal alloys that readily conduct heat. Such metals include aluminum, copper, brass, iron, and steel, and the like, all of which tend to corrode on contact with acidic cleaners. Also, cleaner residue can cause the ice formed immediately after such manual cleaning to be of poor quality.
Despite the cleaning techniques described above, contamination of the ice-forming water supply within the ice machine continues to be a problem. This is especially true given the increased sanitary requirements now in place for ice making machines and other commercial food preparation systems. In particular, condensate run-off from the rear of the evaporator continues to challenge machine designers. Left unattended, condensate from the rear of the evaporator simply runs down the back of the evaporator and either collects in machine recesses below the evaporator, or is channeled back into the water sump. While the condensate itself is clean, it forms on the back of the evaporator plate, which is not easily cleaned in most ice making machines. Hence, the condensate can become contaminated. Drain systems have proven difficult to incorporate into the machine and are not completely effective at removing contamination. Attempts to seal the rear side of the evaporator with foam or other hermetic sealing techniques to prevent condensation have proven to be costly and impractical from the stand point of moisture trapping within the sealing material. Simply evaporating the condensate using heat from the on-board ice refrigeration system with additional air circulation has also proven impractical.